In fluid handling, whether liquid or gas, it is frequently necessary to attach a branch fitting to a pipe sidewall. When the fitting is attached to a pipe under pressure systems are available for securing a short length branch fitting, such as a nipple, to the pipe after which an opening is drilled within the nipple through the pipe sidewall. In instances where the pipe is not under pressure an opening can be first drilled through the pipe sidewall and the inner end of a short length nipple can then be welded to the pipe. If the purpose for attaching the short length nipple is temporary, that is, where it is not attached for continuous and permanent use for the passage of liquid or gas therethrough, it is frequently necessary to close the outer end of the nipple in a way so that it can be easily reopened. For this purpose, a plug is used.
A plug used to close the outer end of a tubular member can be of two basic types, that is, a threaded plug or a non-threaded plug. The use of non-threaded plugs to close the outer end of a pipe are illustrated in previously issued U.S. Pat. Nos. 4,693,278; 4,466,550; 4,058,142; 3,766,947 and 3,155,116. These non-threaded closures typically include a mechanism by which a portion of the closure can be radially outwardly extended into an internal circumferential groove in a tubular member. These type of closures are relatively expensive to manufacture and are used in special applications. The present invention is concerned with a different type of closure member or plug as it is commonly called, that is, the present invention is concerned with a removable externally threaded plug designed to threadably fit into an internally threaded member, such as an internally threaded nipple.
The use of threaded plugs is illustrated in U.S. Pat. No. 5,577,776 entitled "T-Fitting For Lined Pipes", issued Nov. 26, 1996. A further example of the use of a threaded plug is illustrated in FIG. 21 of U.S. Pat. No. 5,560,388 that issued on Oct. 1, 1996, entitled "Seal Plug For Lined Pipelines".
The threaded plugs used to close the interior of a tubular member as illustrated in Pat. Nos. 5,577,776 and 5,560,388 are usually manually inserted into an internally threaded tubular member and then a wrench is inserted into a recess in the upper end of the plug so that the plug can be threadably rotated into sealed position. The present invention is concerned with a plug that is particularly adaptable for insertion into or removal from tubular member by use of a tool, that is, where the plug is secured to the outer end of a specially designed tool by which it is inserted into a tubular member or removed from a tubular member rather than being initially threaded by hand or removed by hand as is the case with the type of threaded plug shown in U.S. Pat. Nos. 5,577,776 and 5,560,388.
It is therefore an objective of this invention to provide a system for closing an opening in the sidewall of a pipe and particularly for a removable plug for an internal threaded opening, such as an internally threaded nipple, the plug being particularly adaptable for insertion or removal by attachment to the outer end of a tool.